[ClusterLabs] Antw: Re: [EXT] Re: Two node cluster without fencing and no split brain?

[john tillman]

> On Mon, Jul 26, 2021 at 4:53 PM john tillman <johnt at panix.com> wrote:
>> >>
>> >> Maybe explain how it should work:
>> >> If the two nodes cannot rech each other, but each can reach the ping
>> >> node,
>> >> which node has the quorum then?
>> >>
>> >
>> > Guess both - which is what is played down as 'disadvantage' in the
>> > description
>> > below ;-)
>> >
>> >
>>
>> It is not perfect, I agree, but it may be better than nothing at all.
>>
>> As for how it worked in my head:
>>
>> I would have used the switch's IP address as the "ping" tie breaker; a
>> common connection point between the two nodes.  My assumption is that if
>> there was network loss by Node A then it would lose quorum. In the mean
>> time Node B would still reach the switch, achieve quorum, and start/move
>> resources.
>>
>
> You seriously misunderstand what "split brain" means. Once more - both
> nodes are up, neither node can contact another node, both nodes can
> ping switch. What should each node do now?
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They would continue running their resources and we would have split brain.

So there is no safe way to support a two node cluster 100% of the time. 
But when all you have are two nodes and a switch ... well, when life gives
you lemons ...

Thank you again for the response and I apologize for beating a dead horse
here.